namespace feng3d
{

    /**
     * 
     * @see http://staffwww.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
     */
    export class SimplexNoise2
    { // Simplex noise in 2D, 3D and 4D

        // 2D simplex noise
        noise2(xin: number, yin: number)
        {
            var n0: number, n1: number, n2: number; // Noise contributions from the three corners
            // Skew the input space to determine which simplex cell we're in
            var s = (xin + yin) * F2; // Hairy factor for 2D
            var i = Math.floor(xin + s);
            var j = Math.floor(yin + s);
            var t = (i + j) * G2;
            var X0 = i - t; // Unskew the cell origin back to (x,y) space
            var Y0 = j - t;
            var x0 = xin - X0; // The x,y distances from the cell origin
            var y0 = yin - Y0;
            // For the 2D case, the simplex shape is an equilateral triangle.
            // Determine which simplex we are in.
            var i1: number, j1: number; // Offsets for second (middle) corner of simplex in (i,j) coords
            if (x0 > y0) { i1 = 1; j1 = 0; } // lower triangle, XY order: (0,0)->(1,0)->(1,1)
            else { i1 = 0; j1 = 1; } // upper triangle, YX order: (0,0)->(0,1)->(1,1)
            // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
            // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
            // c = (3-sqrt(3))/6
            var x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
            var y1 = y0 - j1 + G2;
            var x2 = x0 - 1.0 + 2.0 * G2; // Offsets for last corner in (x,y) unskewed coords
            var y2 = y0 - 1.0 + 2.0 * G2;
            // Work out the hashed gradient indices of the three simplex corners
            var ii = i & 255;
            var jj = j & 255;
            var gi0 = perm[ii + perm[jj]] % 12;
            var gi1 = perm[ii + i1 + perm[jj + j1]] % 12;
            var gi2 = perm[ii + 1 + perm[jj + 1]] % 12;

            // Calculate the contribution from the three corners
            var t0 = 0.5 - x0 * x0 - y0 * y0;
            if (t0 < 0) n0 = 0.0;
            else
            {
                t0 *= t0;
                n0 = t0 * t0 * dot2(grad3[gi0], x0, y0); // (x,y) of grad3 used for 2D gradient
            }
            var t1 = 0.5 - x1 * x1 - y1 * y1;
            if (t1 < 0) n1 = 0.0;
            else
            {
                t1 *= t1;
                n1 = t1 * t1 * dot2(grad3[gi1], x1, y1);
            }

            var t2 = 0.5 - x2 * x2 - y2 * y2;
            if (t2 < 0) n2 = 0.0;
            else
            {
                t2 *= t2;
                n2 = t2 * t2 * dot2(grad3[gi2], x2, y2);
            }
            // Add contributions from each corner to get the final noise value.
            // The result is scaled to return values in the interval [-1,1].
            return 70.0 * (n0 + n1 + n2);
        }
        // 3D simplex noise
        noise3(xin: number, yin: number, zin: number)
        {
            var n0: number, n1: number, n2: number, n3: number; // Noise contributions from the four corners
            // Skew the input space to determine which simplex cell we're in
            var s = (xin + yin + zin) * F3; // Very nice and simple skew factor for 3D
            var i = Math.floor(xin + s);
            var j = Math.floor(yin + s);
            var k = Math.floor(zin + s);
            var t = (i + j + k) * G3;
            var X0 = i - t; // Unskew the cell origin back to (x,y,z) space
            var Y0 = j - t;
            var Z0 = k - t;
            var x0 = xin - X0; // The x,y,z distances from the cell origin
            var y0 = yin - Y0;
            var z0 = zin - Z0;
            // For the 3D case, the simplex shape is a slightly irregular tetrahedron.
            // Determine which simplex we are in.
            var i1: number, j1: number, k1: number; // Offsets for second corner of simplex in (i,j,k) coords
            var i2: number, j2: number, k2: number; // Offsets for third corner of simplex in (i,j,k) coords
            if (x0 >= y0)
            {
                if (y0 >= z0)
                { i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // X Y Z order
                else if (x0 >= z0) { i1 = 1; j1 = 0; k1 = 0; i2 = 1; j2 = 0; k2 = 1; } // X Z Y order
                else { i1 = 0; j1 = 0; k1 = 1; i2 = 1; j2 = 0; k2 = 1; } // Z X Y order
            }
            else
            { // x0<y0
                if (y0 < z0) { i1 = 0; j1 = 0; k1 = 1; i2 = 0; j2 = 1; k2 = 1; } // Z Y X order
                else if (x0 < z0) { i1 = 0; j1 = 1; k1 = 0; i2 = 0; j2 = 1; k2 = 1; } // Y Z X order
                else { i1 = 0; j1 = 1; k1 = 0; i2 = 1; j2 = 1; k2 = 0; } // Y X Z order
            }
            // A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
            // a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
            // a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
            // c = 1/6.

            var x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
            var y1 = y0 - j1 + G3;
            var z1 = z0 - k1 + G3;
            var x2 = x0 - i2 + 2.0 * G3; // Offsets for third corner in (x,y,z) coords
            var y2 = y0 - j2 + 2.0 * G3;
            var z2 = z0 - k2 + 2.0 * G3;
            var x3 = x0 - 1.0 + 3.0 * G3; // Offsets for last corner in (x,y,z) coords
            var y3 = y0 - 1.0 + 3.0 * G3;
            var z3 = z0 - 1.0 + 3.0 * G3;
            // Work out the hashed gradient indices of the four simplex corners
            var ii = i & 255;
            var jj = j & 255;
            var kk = k & 255;
            var gi0 = perm[ii + perm[jj + perm[kk]]] % 12;
            var gi1 = perm[ii + i1 + perm[jj + j1 + perm[kk + k1]]] % 12;
            var gi2 = perm[ii + i2 + perm[jj + j2 + perm[kk + k2]]] % 12;
            var gi3 = perm[ii + 1 + perm[jj + 1 + perm[kk + 1]]] % 12;
            // Calculate the contribution from the four corners
            var t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0;
            if (t0 < 0) n0 = 0.0;
            else
            {
                t0 *= t0;
                n0 = t0 * t0 * dot3(grad3[gi0], x0, y0, z0);
            }
            var t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1;
            if (t1 < 0) n1 = 0.0;
            else
            {
                t1 *= t1;
                n1 = t1 * t1 * dot3(grad3[gi1], x1, y1, z1);
            }
            var t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2;
            if (t2 < 0) n2 = 0.0;
            else
            {
                t2 *= t2;
                n2 = t2 * t2 * dot3(grad3[gi2], x2, y2, z2);
            }

            var t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3;
            if (t3 < 0) n3 = 0.0;
            else
            {
                t3 *= t3;
                n3 = t3 * t3 * dot3(grad3[gi3], x3, y3, z3);
            }
            // Add contributions from each corner to get the final noise value.
            // The result is scaled to stay just inside [-1,1]
            return 32.0 * (n0 + n1 + n2 + n3);
        }

        // 4D simplex noise
        noise4(x: number, y: number, z: number, w: number)
        {
            var n0: number, n1: number, n2: number, n3: number, n4: number; // Noise contributions from the five corners
            // Skew the (x,y,z,w) space to determine which cell of 24 simplices we're in
            var s = (x + y + z + w) * F4; // Factor for 4D skewing
            var i = Math.floor(x + s);
            var j = Math.floor(y + s);
            var k = Math.floor(z + s);
            var l = Math.floor(w + s);
            var t = (i + j + k + l) * G4; // Factor for 4D unskewing
            var X0 = i - t; // Unskew the cell origin back to (x,y,z,w) space
            var Y0 = j - t;
            var Z0 = k - t;
            var W0 = l - t;
            var x0 = x - X0; // The x,y,z,w distances from the cell origin
            var y0 = y - Y0;
            var z0 = z - Z0;
            var w0 = w - W0;
            // For the 4D case, the simplex is a 4D shape I won't even try to describe.
            // To find out which of the 24 possible simplices we're in, we need to
            // determine the magnitude ordering of x0, y0, z0 and w0.
            // The method below is a good way of finding the ordering of x,y,z,w and
            // then find the correct traversal order for the simplex we’re in.
            // First, six pair-wise comparisons are performed between each possible pair
            // of the four coordinates, and the results are used to add up binary bits
            // for an integer index.
            var c1 = (x0 > y0) ? 32 : 0;
            var c2 = (x0 > z0) ? 16 : 0;
            var c3 = (y0 > z0) ? 8 : 0;
            var c4 = (x0 > w0) ? 4 : 0;
            var c5 = (y0 > w0) ? 2 : 0;
            var c6 = (z0 > w0) ? 1 : 0;
            var c = c1 + c2 + c3 + c4 + c5 + c6;

            var i1: number, j1: number, k1: number, l1: number; // The integer offsets for the second simplex corner
            var i2: number, j2: number, k2: number, l2: number; // The integer offsets for the third simplex corner
            var i3: number, j3: number, k3: number, l3: number; // The integer offsets for the fourth simplex corner
            // simplex[c] is a 4-vector with the numbers 0, 1, 2 and 3 in some order.
            // Many values of c will never occur, since e.g. x>y>z>w makes x<z, y<w and x<w
            // impossible. Only the 24 indices which have non-zero entries make any sense.
            // We use a thresholding to set the coordinates in turn from the largest magnitude.
            // The number 3 in the "simplex" array is at the position of the largest coordinate.
            i1 = simplex[c][0] >= 3 ? 1 : 0;
            j1 = simplex[c][1] >= 3 ? 1 : 0;
            k1 = simplex[c][2] >= 3 ? 1 : 0;
            l1 = simplex[c][3] >= 3 ? 1 : 0;
            // The number 2 in the "simplex" array is at the second largest coordinate.
            i2 = simplex[c][0] >= 2 ? 1 : 0;
            j2 = simplex[c][1] >= 2 ? 1 : 0;

            k2 = simplex[c][2] >= 2 ? 1 : 0;
            l2 = simplex[c][3] >= 2 ? 1 : 0;
            // The number 1 in the "simplex" array is at the second smallest coordinate.
            i3 = simplex[c][0] >= 1 ? 1 : 0;
            j3 = simplex[c][1] >= 1 ? 1 : 0;
            k3 = simplex[c][2] >= 1 ? 1 : 0;
            l3 = simplex[c][3] >= 1 ? 1 : 0;
            // The fifth corner has all coordinate offsets = 1, so no need to look that up.
            var x1 = x0 - i1 + G4; // Offsets for second corner in (x,y,z,w) coords
            var y1 = y0 - j1 + G4;
            var z1 = z0 - k1 + G4;
            var w1 = w0 - l1 + G4;
            var x2 = x0 - i2 + 2.0 * G4; // Offsets for third corner in (x,y,z,w) coords
            var y2 = y0 - j2 + 2.0 * G4;
            var z2 = z0 - k2 + 2.0 * G4;
            var w2 = w0 - l2 + 2.0 * G4;
            var x3 = x0 - i3 + 3.0 * G4; // Offsets for fourth corner in (x,y,z,w) coords
            var y3 = y0 - j3 + 3.0 * G4;
            var z3 = z0 - k3 + 3.0 * G4;
            var w3 = w0 - l3 + 3.0 * G4;
            var x4 = x0 - 1.0 + 4.0 * G4; // Offsets for last corner in (x,y,z,w) coords
            var y4 = y0 - 1.0 + 4.0 * G4;
            var z4 = z0 - 1.0 + 4.0 * G4;
            var w4 = w0 - 1.0 + 4.0 * G4;

            // Work out the hashed gradient indices of the five simplex corners
            var ii = i & 255;
            var jj = j & 255;
            var kk = k & 255;
            var ll = l & 255;
            var gi0 = perm[ii + perm[jj + perm[kk + perm[ll]]]] % 32;
            var gi1 = perm[ii + i1 + perm[jj + j1 + perm[kk + k1 + perm[ll + l1]]]] % 32;
            var gi2 = perm[ii + i2 + perm[jj + j2 + perm[kk + k2 + perm[ll + l2]]]] % 32;
            var gi3 = perm[ii + i3 + perm[jj + j3 + perm[kk + k3 + perm[ll + l3]]]] % 32;
            var gi4 = perm[ii + 1 + perm[jj + 1 + perm[kk + 1 + perm[ll + 1]]]] % 32;
            // Calculate the contribution from the five corners
            var t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0 - w0 * w0;
            if (t0 < 0) n0 = 0.0;
            else
            {
                t0 *= t0;
                n0 = t0 * t0 * dot4(grad4[gi0], x0, y0, z0, w0);
            }
            var t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1 - w1 * w1;
            if (t1 < 0) n1 = 0.0;
            else
            {
                t1 *= t1;
                n1 = t1 * t1 * dot4(grad4[gi1], x1, y1, z1, w1);
            }
            var t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2 - w2 * w2;
            if (t2 < 0) n2 = 0.0;
            else
            {
                t2 *= t2;
                n2 = t2 * t2 * dot4(grad4[gi2], x2, y2, z2, w2);
            }

            var t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3 - w3 * w3;
            if (t3 < 0) n3 = 0.0;
            else
            {
                t3 *= t3;
                n3 = t3 * t3 * dot4(grad4[gi3], x3, y3, z3, w3);
            }
            var t4 = 0.6 - x4 * x4 - y4 * y4 - z4 * z4 - w4 * w4;
            if (t4 < 0) n4 = 0.0;
            else
            {
                t4 *= t4;
                n4 = t4 * t4 * dot4(grad4[gi4], x4, y4, z4, w4);
            }
            // Sum up and scale the result to cover the range [-1,1]
            return 27.0 * (n0 + n1 + n2 + n3 + n4);
        }
    }

    const F2 = 0.5 * (Math.sqrt(3.0) - 1.0);
    const G2 = (3.0 - Math.sqrt(3.0)) / 6.0;

    const F3 = 1.0 / 3.0;
    const G3 = 1.0 / 6.0; // Very nice and simple unskew factor, too

    // The skewing and unskewing factors are hairy again for the 4D case
    const F4 = (Math.sqrt(5.0) - 1.0) / 4.0;
    const G4 = (5.0 - Math.sqrt(5.0)) / 20.0;

    const grad3 = [
        [1, 1, 0], [- 1, 1, 0], [1, -1, 0],
        [-1, -1, 0], [1, 0, 1], [-1, 0, 1],
        [1, 0, -1], [-1, 0, -1], [0, 1, 1],
        [0, -1, 1], [0, 1, -1], [0, -1, -1]
    ];

    const grad4 = [[0, 1, 1, 1], [0, 1, 1, - 1], [0, 1, - 1, 1], [0, 1, - 1, - 1],
    [0, - 1, 1, 1], [0, - 1, 1, - 1], [0, - 1, - 1, 1], [0, - 1, - 1, - 1],
    [1, 0, 1, 1], [1, 0, 1, - 1], [1, 0, - 1, 1], [1, 0, - 1, - 1],
    [- 1, 0, 1, 1], [- 1, 0, 1, - 1], [- 1, 0, - 1, 1], [- 1, 0, - 1, - 1],
    [1, 1, 0, 1], [1, 1, 0, - 1], [1, - 1, 0, 1], [1, - 1, 0, - 1],
    [- 1, 1, 0, 1], [- 1, 1, 0, - 1], [- 1, - 1, 0, 1], [- 1, - 1, 0, - 1],
    [1, 1, 1, 0], [1, 1, - 1, 0], [1, - 1, 1, 0], [1, - 1, - 1, 0],
    [- 1, 1, 1, 0], [- 1, 1, - 1, 0], [- 1, - 1, 1, 0], [- 1, - 1, - 1, 0]];

    const p = [
        151, 160, 137, 91, 90, 15,
        131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
        190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
        88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
        77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
        102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
        135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
        5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
        223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
        129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
        251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
        49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
        138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180];


    // To remove the need for index wrapping, double the permutation table length
    const perm = p.concat(p);
    // A lookup table to traverse the simplex around a given point in 4D.
    // Details can be found where this table is used, in the 4D noise method.
    const simplex = [
        [0, 1, 2, 3], [0, 1, 3, 2], [0, 0, 0, 0], [0, 2, 3, 1], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [1, 2, 3, 0],
        [0, 2, 1, 3], [0, 0, 0, 0], [0, 3, 1, 2], [0, 3, 2, 1], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [1, 3, 2, 0],
        [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
        [1, 2, 0, 3], [0, 0, 0, 0], [1, 3, 0, 2], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [2, 3, 0, 1], [2, 3, 1, 0],
        [1, 0, 2, 3], [1, 0, 3, 2], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [2, 0, 3, 1], [0, 0, 0, 0], [2, 1, 3, 0],
        [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
        [2, 0, 1, 3], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [3, 0, 1, 2], [3, 0, 2, 1], [0, 0, 0, 0], [3, 1, 2, 0],
        [2, 1, 0, 3], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [3, 1, 0, 2], [0, 0, 0, 0], [3, 2, 0, 1], [3, 2, 1, 0]];

    function dot2(g: number[], x: number, y: number)
    {
        return g[0] * x + g[1] * y;
    }
    function dot3(g: number[], x: number, y: number, z: number)
    {
        return g[0] * x + g[1] * y + g[2] * z;
    }
    function dot4(g: number[], x: number, y: number, z: number, w: number)
    {
        return g[0] * x + g[1] * y + g[2] * z + g[3] * w;
    }
}